The present invention relates to a semiconductor device comprising a reference voltage generating circuit.
A reference voltage used inside a semiconductor device is required to be stable and independent of the manufacturing process of the semiconductor device, external power source voltage, and operating temperature. As a circuit to generate a reference voltage, a band-gap reference (BGR) circuit (for example, see Y. Okuda et al., “A trimming-Free CMOS Bandgap-Reference Circuit with Sub-1-V-Supply Voltage Operation”, 2007 Symposium on VLSI Circuits Digest of Technical Papers, p. 96-97) is used frequently.
The BGR circuit generates a voltage that does not depend on temperature by adding a voltage having positive temperature dependence and a voltage having negative temperature dependence at an appropriate ratio. In order to fine-adjust the addition ratio, a trimming resistor circuit is provided in the BGR circuit.
As a method of trimming a resistor circuit, a method of physically performing trimming by using a laser fuse etc. and a method of performing trimming by software are known. In the method that uses software, a trimming code is stored in advance in a nonvolatile semiconductor memory that can be rewritten electrically and when a semiconductor device is initialized, a resistance value of the resistor circuit is set according to the trimming code read from the memory.